Plasma-Assisted Catalyst Active Phase Regeneration in Formate-Selective Carbon Dioxide Electroreduction

Abstract

Electrochemical carbon dioxide conversion to more valuable products such as formate (its protonation leads to formic acid, a versatile liquid fuel) is an appealing approach to mitigating the greenhouse gas emission and storing a surplus of renewable energy, but the catalysts developed to date are typically plagued by rapid deactivation. Catalyst deactivation often results in a very low selectivity, in the form of a multitude of products, including H 2 , formate, methanol, CO, and hydrocarbons instead of more preferably a single product, which normally originates from CO-induced phase transformation of hydride catalyst active phases (e.g., Pd hydride). This phase transformation is typically manifested by a high sensitivity of Faradaic Efficiency (FE) and catalyst active phase to small changes of potentials, pH, and temperature. Despite recent developments in catalysts for electrochemical CO 2 conversion, least effort has been devoted to regenerating catalyst active phases, especially for Pd-based catalysts when they are targeted for converting CO 2 to formate. Effective regeneration of the catalyst active phase would allow enhanced efficiency and catalytic activity in CO 2 conversion, greater supply of formate as a fuel, and reduced greenhouse effect. To address the above issues, non-thermal plasma has been utilized to regenerate the hydride catalyst active phase by exacting H from water and assisting in H sorption, and thus eliminate the CO-induced phase transformation through the repulsive interaction between CO and H. This work intends to establish a new framework of multi-electron/proton and heterogeneous electrochemical kinetics driven/mediated by free charged species in plasma.